KR20050095844A - Improved method for the continuous production of alkyl(meth)acrylates with multiple catalyst recycling - Google Patents

Abstract

The invention relates to an improved method for the continuous production of alkyl(methyl)acrylates by transesterification of methyl(meth)acrylate with alcohols that are heavy in comparison with methanol. A special processing technique makes it possible to obtain new levels of product quality. Very high space-time- overall yields can also be obtained. The invention is characterized by the multiple use of a homogeneous catalyst which thereby reduces the costs of auxiliary agents significantly.

Description

Improved method for the continuous production of alkyl (meth) acrylates with multiple catalyst recycling}

The present invention further provides for continuously preparing alkyl (meth) acrylate (C) by releasing methanol (D) by continuously transesterifying methyl (meth) acrylate (A) with alcohol (B) according to Scheme 1. To an improved method.

In Scheme 1 above,

R ² is a straight, branched or cyclic alkyl or aryl radical having 2 to 12 carbon atoms.

R ² groups are, for example, ethyl, n-propyl, isopropyl, allyl, n-butyl, 1-methylpropyl, 2-methylpropyl, tertiary butyl, n-pentyl, 1-methylbutyl, 2-methyl Butyl, 3-methylbutyl, 2,2-dimethylpropyl, n-hexyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1,1-dimethylbutyl, 2,2-dimethyl Butyl, 3,3-dimethylbutyl, 1,2-dimethylbutyl, n-heptyl, 1-methylhexyl, 2-methylhexyl, 3-methylhexyl, 4-methylhexyl, 1,2-dimethylpentyl, 1,3 -Dimethylpentyl, 1,1-dimethylpentyl, 1,1,2,2-tetramethylpropyl, benzyl, n-octyl, 2-ethylhexyl, n-nonyl, 1-methyloctyl, 2-methyloctyl, n- Decyl, n-undecyl, 1-methyldecyl, 2-methyldecyl, n-dodecyl, 2,4-diethyloctyl, cyclopentyl, cyclohexyl, 4-tert butylcyclohexyl, cycloheptyl, cyclododecyl , 2- (dimethylamino) ethyl, 3- (dimethylamino) propyl, 4- (dimethylamino) butyl, 5- (dimethylamino) pentyl, 6- (dimethylamino) hexyl, 8- (dimethylami) No) octyl, 10- (dimethylamino) decyl, 12- (dimethylamino) dodecyl, 2- (diethylamino) ethyl, 3- (diethylamino) propyl, 4- (diethylamino) butyl, 5- (Diethylamino) pentyl, 6- (diethylamino) hexyl, 8- (diethylamino) octyl, 10- (diethylamino) decyl, 12- (diethylamino) dodecyl, 2- (di (iso Propyl) amino) ethyl, 3- (di (isopropyl) amino) propyl, 4- (di (isopropyl) amino) butyl, 5- (di (isopropyl) amino) pentyl, 6-di (isopropyl) amino ) Hexyl, 8- (di (isopropyl) amino) octyl, 10- (di (isopropyl) amino) decyl, 12- (di (isopropyl) amino) dodecyl, 2- (dibutylamino) ethyl, 3 -(Dibutylamino) propyl, 4- (dibutylamino) butyl, 5- (dibutylamino) pentyl, 6- (dibutylamino) hexyl, 8- (dibutylamino) octyl, 10- (dibutylamino ) Decyl, 12- (dibutylamino) dodecyl, 2- (dihexylamino) ethyl, 3- (dihexylamino) propyl, 4- (dihexylamino) butyl, 5- (dihexylamino) pentyl, 6- (dihexylamino) hexyl, 8- (dihexylamino) octyl, 10- (dihexylamino) decyl, 12- (dihexylamino) dodecyl, 2- (methyl Ethylamino) ethyl, 2- (methylpropylamino) ethyl, 2- (methylisopropylamino) ethyl, 2- (methylbutylamino) ethyl, 2- (methylhexyl-amino) ethyl, 2- (methyloctylamino) Ethyl, 2- (ethylpropylamino) ethyl, 2- (ethylisopropylamino) ethyl, 2- (ethylbutylamino) ethyl, 2- (ethylhexyl-amino) ethyl, 2- (ethyloctylamino) ethyl, 3 -(Methylethylamino) propyl, 3- (methylpropyl amino) propyl, 3- (methylisopropylamino) propyl, 3- (methylbutylamino) propyl, 3- (methylhexyl-amino) propyl, 3- (methyl Octylamino) propyl, 3- (ethylpropylamino) propyl, 3- (ethylisopropylamino) propyl, 3- (ethylbutyl amino) propyl, 3- (ethylhexyl-amino) propyl, 3- (ethyloctylamino) Propyl, 4- (methylethylamino) butyl , 4- (methylpropylamino) butyl, 4- (methylisopropylamino) butyl, 4- (methylbutylamino) butyl, 4- (methylhexyl-amino) butyl, 4- (methyloctylamino) butyl, 4- (Ethylpropylamino) butyl, 4- (ethylisopropylamino) butyl, 4- (ethylbutylamino) butyl, 4- (ethylhexyl-amino) butyl, 4- (ethyloctylamino) butyl, 2- (N- Piperidinyl) ethyl, 3- (N-piperidinyl) propyl, 4- (N-piperidinyl) butyl, 5- (N-piperidinyl) pentyl, 6- (N-piperidinyl) hexyl, 8- (N-piperidinyl) octyl, 10- (N-piperidinyl) decyl, 12- (N-piperidinyl) dodecyl, 2- (N-pyrrolidinyl) ethyl, 3- (N- Pyrrolidinyl) propyl, 4- (N-pyrrolidinyl) butyl, 5- (N-pyrrolidinyl) pentyl, 6- (N-pyrrolidinyl) hexyl, 8- (N-pyrrolidinyl) octyl, 10- (N-pyrrolidinyl) decyl, 12- (N-pyrrolidinyl) dodecyl, 2- (N-morpholino) ethyl, 3- (N-morpholino) propyl, 4- (N- Morpholino) butyl, 5- (N-morpholino) pentyl, 6- (N-morpholino) hexyl, 8- (N-morphol) Lino) octyl, 10- (N-morpholino) decyl, 12- (N-morpholino) dodecyl, 2- (N'-methylN-piperazinyl) ethyl, 3- (N'-methyl- N-piperazinyl) propyl, 4- (N'-methyl-N-piperazinyl) butyl, 5- (N'-methyl-N-piperazinyl) pentyl, 6- (N'-methyl-N- Piperazinyl) hexyl, 8- (N'-methyl-N-piperazinyl) octyl, 10- (N'-methyl-N-piperazinyl) decyl, 12- (N'-methyl-N-pipera Genyl) dodecyl, 2- (N'-ethyl-N-piperazinyl) ethyl, 3- (N'-ethyl-N-piperazinyl) propyl, 4- (N'-ethyl-N-piperazinyl ) Butyl, 5- (N'-ethyl-N-piperazinyl) pentyl, 6- (N'-ethyl-N-piperazinyl) hexyl, 8- (N'-ethyl-N-piperazinyl) octyl , 10- (N'-ethyl-N-piperazinyl) decyl, 12- (N'-ethyl-N-piperazinyl) dodecyl, 2- (N'-isopropyl-N-piperazinyl) ethyl , 3- (N'-isopropyl-N-piperazinyl) propyl, 4- (N'-isopropyl-N-piperazinyl) butyl, 5- (N'-isopropyl-N-piperazinyl) Pentyl, 6- (N'-isopropyl-N-piperazinyl) hexyl, 8- (N'-isopropyl-N-piperazinyl) Octyl, 10- (N'-isopropyl-N-piperazinyl) decyl, 12- (N'-isopropyl-N-piperazinyl) dodecyl, 3-oxabutyl, 3-oxapentyl, 2,2 -Dimethyl-4-oxapentyl, 3,6-dioxa-heptyl, 3,6-dioxaoctyl, 3,6,9-trioxadecyl, 3,6,9-trioxoundecyl, 4-oxapentyl , 4-oxahexyl, 4-oxaheptyl, 4,8-dioxanyl, 4,8-dioxadecyl, 4,8-dioxoundecyl, 5-oxahexyl or 5,10-dioxoundecyl group to be.

R ² OH may also be an ethoxylated and / or propoxylated alcohol, and also a mixture of ethoxylated / propoxylated alcohols, for example R ⁵ — (0-CH ₂ —CH ₂ ) _x —OH or R ^5- (0-CH (CH ₃ ) -CH ₂ ) _x -OH or R ^5- (0-CH ₂ -CH (CH ₃ )) _x -OH, wherein R ⁵ is C ₁ to C ₂₀ -alkyl , x is an integer from 10 to 20 or ethoxylated and / or propoxylated amino alcohol R ³ ₂ N (-CH ₂ -CH ₂ -0) _y -H, R ³ ₂ N (-CH (CH ₃ ) CH ₂ -0) _y -H or R ³ ₂ N (-CH ₂ CH (CH ₃ ) -0) _y -H (where y is an integer of 1 to 4, R ³ is an alkyl group having 1 to 6 carbon atoms, The nitrogen atom may also form a 5-7 membered ring with the R ³ substituent) The ring may also be optionally substituted with one or more short-chain alkyl groups, for example methyl, ethyl or propyl.

In the process according to the invention, preference is given to using n-butanol, isobutanol and 2-ethylhexanol.

An improvement over the prior art is that homogeneous tetraalkyl titanate (tetraalkoxytitanium) catalysts which are used preferentially can be surprisingly used repeatedly by recycling. This significantly reduces catalyst consumption and consequently reduces the cost of the adjuvant, which also obviously increases the economic viability of the process.

Prior art

Alkyl (meth) acrylates can be prepared in various ways by transesterification of methyl (meth) acrylate in the presence of a catalyst.

EP 0 960 877 (Elf Atochem S. A.) describes a process for the continuous production of methacrylate esters of dialkylamino alcohols. Dialkylamino alcohols are generally reacted with methyl (meth) acrylates to give dialkylaminoalkyl (meth) acrylates by the following process.

The mixture of starting materials (methyl (meth) acrylate and dialkylamino alcohol) may be a homogeneous tetraalkyl titanate transesterification catalyst such as tetrabutyl titanate, tetraethyl titanate or tetra (2-ethylhexyl) titanate] And one or more polymerization inhibitors (e.g., pentothiazine, tertiary butylcatechol, hydroquinone monomethyl ether or hydroquinone), continuously fed to the stirred reactor and continuously removing the methyl (meth) acrylate / methanol azeotrope mixture. While converted to dialkylamino (meth) acrylate in a stirred reactor at a temperature of 90-120 ° C. Crude reaction mixture (crude ester) is fed to the first distillation tube, a substantially catalyst-free stream is recovered upwards under reduced pressure, and the catalyst and also a small amount of dialkylaminoalkyl (meth) acrylate are removed from the bottom of the distillation tube. do. The top stream of the first distillation tube is then fed to a second distillation tube and the low boiling product stream comprising a small amount of dialkylaminoalkyl (meth) acrylate under reduced pressure is recovered upwards, predominantly dialkylaminoalkyl (meth The stream consisting of) acrylate and polymerization inhibitor (s) is removed at the bottom and fed to a third distillation tube. In a third distillation tube, rectification is carried out under reduced pressure, the desired pure dialkylaminoalkyl (meth) acrylate ester is recovered upwards and essentially the polymerization inhibitor (s) is recovered at the bottom. After further purification using a film evaporator, the bottoms stream of the first distillation tube is recycled to the reactor and the top stream is likewise removed from the second distillation tube.

Details of the recycling process of homogeneous catalysts are not listed. This can only be recognized from the specified purification of the bottom effluent of the first distillation tube using a film evaporator where only the remaining dialkylaminoalkyl (meth) acrylates are removed from the catalyst and the high boiling secondary components and recycled to the reactor.

EP 0 968 995 (Mitsuibishi Gas Chemical Comp.) Describes a process for the continuous production of alkyl (meth) acrylic esters using a reaction column. The transesterification reaction is carried out directly in the distillation column [ie, the distillation tube and reactor for removing methyl (meth) acrylate / methanol azeotrope form one device), the starting material [methyl (meth) acrylate and alcohol] Is fed continuously. Likewise herein an essential catalyst which is preferably a titanium compound is present in the distillation tube. In the case of a continuous catalyst, the catalyst is continuously metered into the distillation tube. However, when the homogeneous catalyst is used in the distillation tube due to the washing effect of the liquid reflux in the distillation tube, the catalyst demand increases, and when the solid catalyst precipitate occurs, the inside of the column becomes dirty. In the case of heterogeneous catalysts, the catalyst is present in the reaction column. However, placing the catalyst in the distillation tube is disadvantageous because the pressure drop in the distillation tube is increased, and the additional cost is greatly increased and inconvenience is caused by the regular cleaning of the distillation tube. In addition, heterogeneous catalysts can be inert, for example by undesirable polymerization.

There is no information on the process of preliminary removal of crude esters and then recycling the homogeneous catalyst into the reaction column.

Compared to the above-mentioned process, German Patent Publication No. 102 00 171.5 discloses a clearly improved continuous process for the preparation of alkyl (meth) acrylates by transesterifying methyl (meth) acrylates with alcohols having a higher boiling point than methanol. [Fig. 1].

The reactant methyl (meth) acrylate (MMA) 11 and alcohol 12 are continuously fed to a suitable reaction device 1 which may be a single reaction tank or two or more reaction tank batteries connected in series. It is preferable that all of the reaction tanks have a vapor takeoff in the azeotropic distillation tube 2 for removing methanol released in the reaction. The homogeneous tetraalkyl titanate catalyst used preferentially (the tetraalkoxytitanium content relative to the MMA used is preferably 0.2 to 0.5% by weight) is continuously metered into the reaction apparatus 1 which is the polymerization inhibitor (s). However, the transesterification catalyst used may also be any transesterification catalyst known by the prior art. Examples of polymerization inhibitors include a mixture of hydroquinone monomethyl ether and oxygen. Since the alcohol used may comprise water (in the case of n-butanol, the amount of water in the alcohol used is 0.05 to 0.005% by weight), so that the alcohol is distilled off using an azeotropic distillation tube (2) prior to introduction into the reactor It is preferable to make it. Water contained in alcohol is removed upwards. In order to avoid contamination of the alcohol and methanol / MMA azeotrope 13 used, alcohol is preferably added to the bottom section of the distillation tube 2. However, the alcohol used may also be dehydrated by treatment with a dehydrating agent, for example molecular sieve, or by using an upstream dehydrating distillation tube by membrane separation, for example by distillation. Dehydration is important because the irreversible loss of catalyst (eg tetraalkyl titanate) in the reactor can be induced by water contained in the alcohol. This dehydration step inhibits hydrolysis of the catalyst and increases costs due to problems caused by solid precipitates and increased catalyst usage. The reaction is carried out in a reaction apparatus in the temperature range of 80 to 160 ° C. The temperature range of 110-135 degreeC is preferable. To positively affect the equilibrium of the reaction, the methanol released from the reaction is removed from the reaction mixture as azeotrope with MMA 13 using distillation tube 2. The reaction mixture consisting mainly of product alkyl (meth) acrylates, unconverted MMA and alcohols with small amounts of methanol, catalysts, polymerization inhibitors and small by-products is a low boiling distillation that is continuously operated after about 0.5 to 3 hours of reactor residence time. It is supplied to the pipe 3 (retention time of 0.75 to 1.5 hours is preferable). The low boiling components for the product esters, mainly methanol, MMA and unconverted reactant alcohols, are preferably removed from the low boiling distillation tube 3 above under reduced pressure in the range of 20 to 200 mbar. These components are removed upwards in the distillation tube and recycled to the reactor zone 14. This circulating stream ensures that the conversion is actually complete for the reactants MMA and the alcohol, based on the overall process. The crude ester (15) obtained at the bottom of the distillation tube (3) and still contaminated with catalyst, polymerization inhibitors and high boiling by-products preferably comprises at least 98% by weight product ester and is operated at a preferred pressure range of 20 to 200 mbar. Additional vacuum distillation steps 4 and 5 are fed continuously during the workup. High purity product esters are continuously distilled off in the distillation stages 4 and 5 as top product 16. When conventional vacuum distillation tubes as described in the prior art are used for the removal of high boiling by-products from catalysts and polymerization inhibitors and coarse esters (15), there is an unacceptably high thermal stress at the bottom of the vacuum distillation tubes. The catalyst decomposes, thus releasing the reactant alcohol and forming its ether. Both compounds (reactants alcohols and ethers thereof) are low boiling components for the product esters and are therefore produced as impurities in the product esters, which obviously degrades the product quality. This problem can be solved by removing the product esters from catalysts and polymerization inhibitors and high boiling by-products using a device where membrane evaporation 5 is gentle. Devices useful for this purpose include falling films, thin films and disconnect evaporators. An additional downstream high boiling distillation step (4) is used to achieve high product ester purity [product ester> 99.9 wt%, alcohol <120 ppm, MMA <10 ppm, ether <5 ppm, color number <apha <1]. In this case, however, one apparatus using membrane evaporation has the disadvantage of performing insufficient purification, so that high boiling by-products are also produced in the pure product ester 16. This problem is solved by placing a vacuum rectifying tube 4 for removing high-boiling by-products from the pure product esters above the device using membrane evaporation. After removing the high boiling by-products from the catalyst and the polymerization inhibitor and the crude ester, certain portions of the product ester remain in the bottom product, so that the bottom effluent can still flow and can be sufficiently transferred. In order to minimize the loss of product esters when releasing catalysts, polymerization inhibitors and high boiling by-products 17, a downstream vacuum evaporation step 6 operating in the preferred pressure range 20 to 200 mbar should be employed. Devices useful for this work are also devices that use membrane evaporation. Devices useful for this purpose also include falling film, thin film and disconnect evaporators. Because of the excessive content of the high boiling point component, the product ester removed in the upper layer in the evaporation step does not meet the requirements for pure product esters. In addition, due to thermal decomposition of the catalyst, it contains the reactant alcohol and sometimes its ethers. For this reason, the purpose of the recovery of the product esters from the distillation stream cannot be achieved by recycling directly into the high boiling distillation tube (4), but is recycled to the reaction apparatus (1) or advantageously to the low boiling distillation tube (3) to obtain a first This can be achieved by removing the low boiling point before the evaporation step 5.

The process is repeatedly subjected to thermal stress, thus removing the partially inert homogeneous catalyst, which is likely to be damaged, from the product ester and then completely released by the polymerization inhibitor and the high boiling by-products and not recycled and reused. Since the catalyst cost is relatively high, the aid cost increases.

German Patent Publication No. 101 27 939 (BASF) describes a continuous transesterification process. One formulation of the partial object to be achieved is that the catalyst must be reused without any problem.

It is an object of the present invention to provide a process that meets the following criteria without the above drawbacks:

1. Starting materials (catalysts, stabilizers, lower (meth) acrylates) should be economical, easy to handle and used in industrial quantities.

2. The catalyst should be stable at elevated temperatures in the presence of a small amount of water.

3. The loss of activity of the catalysts is small and these catalysts should be able to be reused without any problems.

4. No alcohols independent of this system should be introduced into the transesterification reaction via transesterification catalysts.

5. Use of devices that have a long time-on-stream of the device, i.e. have little polymerization problems and require little repair.

6. Direct use or use of the resulting mixture or azeotrope of lower alkanols and corresponding esters.

7. Substantial recovery of useful products remaining from waste streams and by-products.

8. The transesterification reaction should preferably be run continuously.

9. Preferred esters should be of high purity (at least 99.9%) and when dialkylaminomethyl (meth) acrylates are prepared, the formation of ethylene glycol di (meth) acrylate and vinyloxyethyl (meth) acrylate, As much as possible it should be reduced to less than 100 ppm

10. The amount of waste stream is very small and should be easy to handle.

11. Conversion rates and yields must be high (greater than 95%).

12. The residence time should be short.

13. The whole process must be technically simple and economic.

Although this objective is formulated, there is no explanation in explaining the selective recycling of active or semi-active catalysts. In addition, when a fully recycled or partially recycled transesterification catalyst is used, there is no information on any change in product quality or information on the majority of ratios in the recycle of the catalyst.

purpose

It is an object of the present invention to provide a continuous process for transesterification of methyl (meth) acrylate (A) with alcohols (B) having a higher boiling point than methanol (D), wherein the homogeneous catalyst used here is partially recycled and repeated. Can be used. In this case, (meth) acrylic esters or alkyl (meth) acrylates refer to esters and derivatives of acrylic acid or methacrylic acid below. In addition, the novel process should provide products that are of better quality than those already on the market. The novel process further requires that the alkyl (meth) acrylates be prepared in a small, uncomplicated, and powerfully more effective manner (ie cheaper). Although not specifically illustrated in detail, these and further objects derived from further discussion of the introduction of the prior art are achieved with a process as illustrated below.

solution

Surprisingly, the homogeneous tetraalkyl titanate (tetraalkoxytitanium) catalyst, starting from the prior art established by Rohm (German Patent Publication No. 102 00 171.5), is still preferred in the column bottoms and membrane evaporators. Despite the thermal stress it has been found to have significant activity at various points in the process. Therefore, repeated use of the catalyst other than the simple outline is possible. This clearly reduces the cost of the adjuvant with unchanged product quality and unchanged space time and overall yield. For this purpose, further needs are liquid stream dividers and pumps. The amount of catalyst recycled is controlled by using alcohol (B) or MMA (A) conversion in the reaction apparatus 1 as a measure of current catalytic activity. A further indicator that can be used for current catalytic activity is the amount and composition of the low boiling point circulating stream 14. In order to industrially perform the catalyst cycle, the following solutions are generally possible:

Resolution Aspect 1 (FIG. 2):

The bottom effluent of the vacuum evaporation step 6 comprising catalyst, polymerization inhibitor and high boiling by-products and residual product esters is separated and partially recycled to the reaction apparatus 1. The remaining residual stream is discharged (17). The release step 17 is proportional to the steady state amount of the high boiling secondary components that can be formed and is proportional to the remaining residual activity of the catalyst in the bottoms effluent in the vacuum evaporation step 6. The fresh amount of catalyst in stream 11 is reduced in proportion to the amount of catalyst circulated compared to the operation where the catalyst is not recycled.

The recycle stream 18 is 1 to 95% by weight, preferably 40 to 90% and most preferably 60 to 85% by weight of the bottoms effluent from the vacuum evaporation step 6.

Resolution Aspect 2 (FIG. 3):

The bottom effluent is separated from the device using a mild membrane evaporation step (5), which remains after the removal of the very pure product ester and comprises a catalyst, a polymerization inhibitor and a high boiling by-product and a residual product ester, and partially into the reaction device (1). 18 is recycled. The remaining residual stream is fed to the vacuum evaporation stage 6 according to the prior art, where most of the product ester is removed and recycled to the reaction apparatus 1 or advantageously to the low boiling distillation tube 3. The bottoms effluent of the vacuum evaporation step 6 comprising catalyst, polymerization inhibitor and low boiling by-products and residual product esters is discharged (17). The release step 17 is proportional to the steady state amount of the high boiling secondary components formed and is proportional to the remaining residual activity of the catalyst in the bottoms effluent of the vacuum evaporation steps 4, 5. The fresh amount of catalyst in stream 11 is reduced in proportion to the amount of catalyst recycled as compared to the operation where the catalyst is not recycled.

The recycle stream 18 is 1 to 95% by weight, preferably 40 to 90% and most preferably 60 to 85% by weight of the bottoms effluent from the vacuum evaporator 5.

Solution 3 (FIG. 4):

The bottom effluent is separated from the device using a mild membrane evaporation step (5), which remains after the removal of the very pure product ester and comprises a catalyst, a polymerization inhibitor and a high boiling by-product and a residual product ester, and partially into the reaction device (1). 18 is recycled. The remaining residual stream is fed to the vacuum evaporation stage 6 according to the prior art, where most of the product ester is removed and recycled to the reaction apparatus 1 or advantageously to the low boiling distillation tube 3. The bottoms effluent of the vacuum evaporation step 6 comprising catalyst, polymerization inhibitor and low boiling by-products and residual product esters is separated and partially 18 recycled to the reaction apparatus 1. The remaining residual stream is discharged (17). The discharge step 17 is proportional to the steady state amount of the high boiling secondary components formed and to the remaining residual activity of the catalyst in the recycle stream 18. The fresh amount of catalyst in stream 11 is reduced in proportion to the amount of catalyst recycled as compared to the operation where the catalyst is not recycled.

The recycle stream 18 is 1 to 95% by weight, preferably 40 to 90% by weight and most preferably 60 to 85% by weight of the total amount of bottoms effluent from the membrane evaporator 5 and the vacuum evaporator 6.

Example

The process according to the invention is described in detail by the following examples, but is not limited thereto.

The cited examples are carried out in the laboratory on a pilot scale and 5 to 6 kg of product (efficiency per hour: feed (6 to 8 kg of MMA and alcohol) .. The laboratory structure is present in a slightly modified form as shown in FIG. 3.

(Comparative) Example 1: The catalyst is not recycled (preparation of n- / i-butyl methacrylate).

The reactor used was a steam heated stainless steel reactor with a maximum fill volume of 15 liters. The reactor is connected via a steam line to an azeotropic distillation tube 2 mounted above. An azeotropic distillation tube (atmospheric pressure = 1 bar _abs ) is packed with a pilot plant glass tube with a diameter D of 0.1 m and a Sulzer CY structured metal instrument fill with H of 2 m. The feed for the alcohol, which is a reactant, is placed in the middle of the column (H = 1m). The reactor effluent is continuously fed to the low boiling distillation tube (3). This distillation tube is packed with a pilot plant vacuum glass column (atmospheric pressure = 120 mbar _abs ) with a diameter D of 0.1 m and a Sulzer CY structured metal instrument fill with H of 3.8 m. The feed is H 2 m. The bottom is heated by steam. The condensed top takeoff (circulating stream) 14 is continuously recycled to the reactor. Instead of the descent evaporator 5 shown in FIG. 3, the continuous workup of the bottoms effluent of the low boiling distillation tube 15 is carried out using a thermal oil heated glass thin film evaporator having an evaporator surface area A of 0.1 m ² . . The vapor of the glass thin film evaporator is passed continuously to the high boiling distillation tube 4 mounted above. It is packed with a pilot plant vacuum glass column (atmospheric pressure = 120 mbar _abs ) with a diameter D of 0.05 m and a Sulzer EX structured metal instrument fill with H of 3.8 m. The bottoms effluent is continuously fed to a second small thermal oil heated glass thin film evaporator 6 (atmospheric pressure = 120 mbar _abs ) having an evaporator surface area A of 0.02 m ² . The vapor of this second glass thin film evaporator is condensed, mixed with the reactor effluent and fed continuously to the low boiling distillation tube. Bottom effluent 17 is continuously discharged from the process. The reactants (MMA and alcohol) are continuously metered by a piston metering pump, and the catalyst (tetraalkyl titanate) is metered in (in detail, water-free) and dissolved in the MMA feed. The MMA / catalyst feed is fed directly to the reactor and the alcohol feed introduced is preheated (to the internal column temperature) to the center of the azeotropic distillation tube. Continuous addition reaction of the stabilizer solution (0.2 wt% hydroquinone monomethyl ether in MMA or product ester) to the reflux stream of the distillation tube is carried out using a hose pump. Continuous transport of the stream between the parts of the plant is carried out using a piston metering pump or by a vacuum suction effect. The intermediate container (buffer volume) is significantly suppressed as much as possible. The composition of the stream (MMA, alcohol, MeOH and product ester content) is determined using gas chromatography.

To continuously prepare n-butyl methacrylate (n-BuMA), 4 kg / h MMA feed, 18 g / h tetra-n-butyl titanate [Ti (n-OBu) ₄ ] and 2.7 kg / n-BuOH h is metered into the reactor (11). The recycle stream from the top of the low boiling column is also continuously flowed into the reactor (2.8 kg / h of the following composition: 1.0 wt% n-BuMA, 38.3 wt% n-BuOH, 57.3 wt% MMA and 3.4 wt% MeOH). The MMA: n-BuOH molar ratio in the reactor is 1.1: 1. At reaction residence time 1 h and MMA / MeOH azeotropic takeoff 1.5 kg / h, the reactor temperature is obtained at 115 ° C. The composition of the MMA / MeOH azeotrope is less than 82% MeOH, 18% MMA and 5 ppm n-BuOH. The resulting reactor effluent 9 kg / h has the following composition: 64.6 wt% n-BuMA, 13.5 wt% n-BuOH, 20.3 wt% MMA, 1.3 wt% MeOH and 0.3 wt% by-product. Thus, the space time yield of the reactor based on n-BuMA is 570 kg / h / m ³ . By substantially completely removing the low boiling point components for n-BuMA, the bottoms effluent of the low boiling distillation tube is a crude ester (5.8 kg / h) already containing catalyst and stabilizer and an amount greater than 99.8% by weight of n-BuMA. Therefore, the yield of n-BuMA based on the whole process is actually 100%. Likewise, the yield of MMA based on the overall process is actually 100% by subtracting the MMA loss through the previously calculated MMA / MeOH azeotrope. At an evaporation ratio (ratio of vapor stream to feed stream) at about 90% of the first large thin film evaporator, 5.1 kg / h of pure n-BuMA is finally obtained at the top of the high boiling distillation tube and the composition is Equal: 99.92% n-BuMA, 120 ppm n-BuOH, less than 10 ppm MMA, less than 5 ppm di-n-butyl ether, less than 0.2 apha. At an evaporation rate of about 90% of the second small thin film evaporator, the total emissions of the process (catalyst, stabilizer, high boiling by-product, n-BuMA) is 0.1 kg / h and n based on the pure n-BuMA produced. The yield loss of -BuMA is less than 0.5% by weight.

Catalyst consumption is 3.5 g of tetra-n-butyl titanate / kg of pure n-BuMA.

To continuously prepare isobutyl methacrylate (i-BuMA), 3.4 kg / h MMA feed, 19 g / h tetra-i-butyl titanate [Ti (i-OBu) ₄ ] and 2.36 i-BuOH feed kg / h is metered into the reactor. The recycle stream from the top of the low boiling distillation column was also continuously flowed into the reactor [2.4 kg / h of the following composition: 6.2 wt% i-BuMA, 35.3 wt% i-BuOH, 56.3 wt% MMA and 2.2 wt% MeOH]. do. The MMA: i-BuOH molar ratio in the reactor feed is 1.1: 1. At a reaction residence time of 1.2 h and a MMA / MeOH azeotropic takeoff of 1.26 kg / h, the reactor temperature is obtained at 115 ° C. The composition of the MMA / MeOH azeotrope is less than 82% MeOH, 18% MMA and 5 ppm n-BuOH. The resulting reactor effluent 6.9 kg / h has the following composition: 67.3 wt% i-BuMA, 12.0 wt% i-BuOH, 19.4 wt% MMA, 0.8 wt% MeOH and 0.5 wt% by-product. Thus, the space time yield of the reactor based on i-BuMA is 516 kg / h / m ³ . By substantially completely removing the low boiling point components for i-BuMA, the bottoms effluent of the low boiling distillation column is a crude ester (5.0 kg / h) already containing catalyst and stabilizer and an amount greater than 99.5% by weight of i-BuMA. Therefore, the yield of i-BuMA based on the whole process is actually 100%. Likewise, the yield of MMA based on the overall process is actually 100% by subtracting the MMA loss through the previously calculated MMA / MeOH azeotrope. At an evaporation ratio (ratio of vapor stream to feed stream) of about 90% of the first large thin film evaporator, 4.5 kg / h of pure i-BuMA is finally obtained at the top of the high boiling distillation tube and the composition is Equal: 99.9 wt% i-BuMA, 150 ppm i-BuOH, less than 10 ppm MMA, 0 ppm di-i-butyl ether, less than 0.2 apha. At an evaporation rate of about 90% of the second small thin film evaporator, the total emissions of the process (catalyst, stabilizer, high boiling by-product, i-BuMA) are 0.05 kg / h and i based on pure i-BuMA produced. The yield loss of -BuMA is less than 0.5% by weight.

Catalyst consumption is 4.2 g of tetra-i-butyl titanate / kg of pure i-BuMA.

Example 2: Complete recycling of catalyst (preparation of n-butyl methacrylate).

The reactor 1 used is a steam heated stainless steel reactor with a maximum fill volume of 15 liters. The reactor is connected via a steam line to an azeotropic distillation tube 2 mounted above. An azeotropic distillation tube (atmospheric pressure = 1 bar _abs ) is a pilot plant glass tube with a diameter (D) of 0.1 m and packed with a Sulzer CY structured metal instrument fill with H of 2 m. The feed for the alcohol, which is a reactant, is placed in the middle of the column (H = 1m). The reactor effluent is continuously fed to the low boiling distillation tube (3). This distillation tube is packed with a pilot plant vacuum glass column (atmospheric pressure = 120 mbar _abs ) with a diameter D of 0.1 m and a Sulzer CY structured metal instrument fill with H of 3.8 m. The feed is H 2 m. The bottom is heated by steam. The condensed top takeoff (circulating stream) 14 is continuously recycled to the reactor. Instead of the descent evaporator 5 shown in FIG. 3, the continuous workup of the bottoms effluent of the low boiling distillation tube 15 is carried out using a thermal oil heated glass thin film evaporator having an evaporator surface area A of 0.1 m ² . . The vapor of the glass thin film evaporator is passed continuously to the high boiling distillation tube 4 mounted above. It is packed with a pilot plant vacuum glass column (atmospheric pressure = 150 mbar _abs ) with a diameter (D) of 0.05 m and a Sulzer EX structured metal instrument fill with H of 0.5 m. The bottoms effluent is continuously recycled into the reactor 18 and partly discharged continuously from the process 17. At time t of zero hours, the bottoms effluent is completely continuously recycled to the reactor 18, no longer any emissions 17 and no new catalyst metered in. The reactants (MMA and alcohol) are continuously metered by a piston metering pump, and the catalyst (tetraalkyl titanate) is metered in (in detail, water-free) and dissolved in the MMA feed. The MMA / catalyst feed is fed directly to the reactor and the alcohol feed introduced is preheated (to the internal column temperature) to the center of the azeotropic distillation tube. Continuous addition reaction of the stabilizer solution (0.2 wt% hydroquinone monomethyl ether in MMA or product ester) to the reflux stream of the distillation tube is carried out using a hose pump. Continuous transport of the stream between the parts of the plant is carried out using a piston metering pump or by a vacuum suction effect. The intermediate container (buffer volume) is significantly suppressed as much as possible. The composition of the stream (MMA, alcohol, MeOH and product ester content) is determined using gas chromatography.

To continuously prepare n-butyl methacrylate (n-BuMA), 3.8 kg / h MMA feed, 18 g / h tetra-n-butyl titanate [Ti (n-OBu) ₄ ] and 2.7 kg n-BuOH Meter / h into the reactor. The recycle stream from the top of the low boiling distillation column is also continuously flowed into the reactor [3.0 kg / h of the following composition: 0.2% n-BuMA, 31.1% n-BuOH, 66.4% MMA and 1.9% MeOH] . The MMA: n-BuOH molar ratio in the reactor is 1.2: 1. At a reaction residence time of 1 h and MMA / MeOH azeotropic takeoff of 1.4 kg / h, the reactor temperature is obtained at 115 ° C. The composition of the MMA / MeOH azeotrope is less than 80.4 weight percent MeOH, 19.6 weight percent MMA and 5 ppm n-BuOH. The resulting reactor effluent 8.1 kg / h has the following composition: 63.8 wt% n-BuMA, 11.3 wt% n-BuOH, 24.0 wt% MMA, 0.7 wt% MeOH and 0.2 wt% by-product. Thus, the n-BuMA conversion of the reactor is 74%. After releasing at t = 0 and stopping the feed of fresh catalyst, n-BuOH conversion (as indicator for catalyst activity) is performed over 24 hours. As can be seen from Figure 5, the n-BuOH conversion is surprisingly only 18% to 56, even though no high boiling secondary components are released and no new catalyst is fed and the catalyst is recycled about eight times throughout the whole process. % Decreases within 24 hours.

Example 3: Partial recycle of catalyst (preparation of i-butyl methacrylate).

The reactor 1 used is a steam heated stainless steel reactor with a maximum fill volume of 15 liters. The reactor is connected via a steam line to an azeotropic distillation tube 2 mounted above. An azeotropic distillation tube (atmospheric pressure = 1 bar _abs ) is a pilot plant glass tube with a diameter (D) of 0.1 m and packed with a Sulzer CY structured metal instrument fill with H of 2 m. The feed for the alcohol, which is a reactant, is placed in the middle of the column (H = 1m). The reactor effluent is continuously fed to the low boiling distillation tube (3). This distillation tube is packed with a pilot plant vacuum glass column (atmospheric pressure = 120 mbar _abs ) with a diameter D of 0.1 m and a Sulzer CY structured metal instrument fill with H of 3.8 m. The feed is H 2 m. The bottom is heated by steam. The condensed top takeoff (circulating stream) 14 is continuously recycled to the reactor. Instead of the descent evaporator 5 shown in FIG. 3, the continuous workup of the bottoms effluent of the low boiling distillation tube 15 is carried out using a thermal oil heated glass thin film evaporator having an evaporator surface area A of 0.1 m ² . . The vapor of the glass thin film evaporator is passed continuously to the high boiling distillation tube 4 mounted above. It is packed with a pilot plant vacuum glass column (atmospheric pressure = 150 mbar _abs ) with a diameter (D) of 0.05 m and a Sulzer EX structured metal instrument fill with H of 0.5 m. The bottoms effluent is continuously recycled into the reactor 18 and partly discharged continuously from the process 17. The reactants (MMA and alcohol) are continuously metered by a piston metering pump, and the catalyst (tetraalkyl titanate) is metered in (in detail, water-free) and dissolved in the MMA feed. The MMA / catalyst feed is fed directly to the reactor and the alcohol feed introduced is preheated (to the internal column temperature) to the center of the azeotropic distillation tube. Continuous addition reaction of the stabilizer solution (0.2 wt% hydroquinone monomethyl ether in MMA or product ester) to the reflux stream of the distillation tube is carried out using a hose pump. Continuous transport of the stream between the parts of the plant is carried out using a piston metering pump or by a vacuum suction effect. The intermediate container (buffer volume) is significantly suppressed as much as possible. The composition of the stream (MMA, alcohol, MeOH and product ester content) is determined using gas chromatography.

To continuously prepare isobutyl methacrylate (i-BuMA), 2.78 kg / h MMA feed, 3 g / h tetra-i-butyl titanate [Ti (i-OBu) ₄ ] and i-BuOH feed 1.9 kg / h is metered into the reactor. The recycle stream from the top of the low boiling distillation column is also continuously flowed into the reactor (2.2 kg / h of the following composition: 2.8 wt% i-BuMA, 39.3 wt% i-BuOH, 56.2 wt% MMA and 1.7 wt% MeOH). . The MMA: i-BuOH molar ratio in the reactor feed is 1.1: 1. At a reaction residence time of 1.2 h and an MMA / MeOH azeotropic takeoff of 1.04 kg / h, the reactor temperature is obtained at 116 ° C. The composition of the MMA / MeOH azeotrope is less than 79 wt% MeOH, 21 wt% MMA and 5 ppm i-BuOH. The resulting reactor effluent 6.5 kg / h has the following composition: 66.8 wt% i-BuMA, 13.1 wt% n-BuOH, 19.0 wt% MMA, 0.5 wt% MeOH and 0.6 wt% by-product. Thus, the space time yield of the reactor based on i-BuMA is 417 kg / h / m ³ . By actually completely removing the low boiling point components for i-BuMA, the bottoms effluent of the low boiling distillation column is a crude ester (4.25 kg / h) already containing catalyst and stabilizer and an amount greater than 99.5% by weight of i-BuMA. Therefore, the yield of i-BuOH based on the whole process is actually 100%. Likewise, the yield of MMA based on the overall process is actually 100% by subtracting the MMA loss through the previously calculated MMA / MeOH azeotrope. At an evaporation ratio (ratio of vapor stream to feed stream) in a thin film evaporator of about 90%, pure i-BuMA 3.81 kg / h is finally obtained at the top of the high boiling distillation tube and the composition is as follows: i -More than 99.9 weight percent BuMA, 150 ppm n-BuOH, less than 10 ppm MMA, less than 0 ppm di-i-butyl ether, less than 0.2 apa. At 10% emission (0.05 kg / h), ie 90% recycle (0.45 kg / h) of the bottom effluent of the thin film evaporator, the catalyst consumption is 0.8 g of tetra-i-butyl titanate / kg of pure i-BuMA.

Therefore, compared with Example 1, the catalyst saving amount is about 80%.

Description of the reference number:

1. Reactor

2. azeotropic distillation tube

3. Low boiling distillation tube

4. High boiling distillation tube

5. Membrane Evaporator

6. Membrane Evaporator

11.Methyl (meth) acrylate and Catalyst Feed

12. Alcohol Feed

13. Methanol / methyl (meth) acrylate azeotrope

14. Low Boiling Circulation Stream

15. Coarse Ester

16. Pure Ester

17. High boiling point and catalyst

18. Catalyst Recirculation

Claims (15)

A process for continuously producing a higher (meth) acrylic acid ester (C) by transesterifying methyl (meth) acrylate (A) with a higher alcohol (B) in the presence of a catalyst or catalyst mixture, The bottoms effluent of the vacuum evaporation step (6) is separated and partly fed to the reaction apparatus (1). A process for continuously producing a higher (meth) acrylic acid ester (C) by transesterifying methyl (meth) acrylate (A) with a higher alcohol (B) in the presence of a catalyst or catalyst mixture, The bottoms effluent from the membrane evaporator (5) is separated and partially supplied to the reaction apparatus (1). A process for the continuous production of higher (meth) acrylic acid esters (C). A process for continuously producing a higher (meth) acrylic acid ester (C) by transesterifying methyl (meth) acrylate (A) with a higher alcohol (B) in the presence of a catalyst or catalyst mixture, The bottoms effluent from the membrane evaporator 5 is separated and partially supplied to the reaction apparatus 1 and the bottoms effluent of the vacuum evaporation step 6 is separated and fed to the reaction apparatus 1. Process for the continuous production of meth) acrylic acid ester (C). The method according to claim 1, wherein the alcohol used is n-butanol, isobutanol or 2-ethylhexanol. The process according to any one of claims 1 to 3, wherein the catalyst used is a homogeneous catalyst. A process according to claim 5, wherein the catalyst used is titanate of alcohol (B). 2. Process according to claim 1, characterized in that 1 to 95% by weight of bottoms effluent from the vacuum evaporation step (6) is fed to the reaction apparatus. 8. Process according to claim 7, characterized in that 40 to 90% by weight of the bottoms effluent from the vacuum evaporation step (6) is fed to the reaction apparatus (1). 9. Process according to claim 8, characterized in that 60 to 85% by weight of bottoms effluent from the vacuum evaporation step (6) is fed to the reaction device (1). 3. Process according to claim 2, characterized in that 1 to 95% by weight of bottoms effluent from the membrane evaporator (5) is fed to the reaction device (1). Process according to claim 10, characterized in that 40 to 90% by weight of bottoms effluent from the membrane evaporator (5) is fed to the reaction device (1). Process according to claim 11, characterized in that 60 to 85% by weight of bottoms effluent from the membrane evaporator (5) is fed to the reaction device (1). 4. Process according to claim 3, characterized in that 1 to 95% by weight of the bottoms effluent from the membrane evaporator (5) and the vacuum evaporation step (6) is fed to the reaction apparatus (1). 14. Process according to claim 13, characterized in that 40 to 90% by weight of the bottoms effluent from the membrane evaporator (5) and the vacuum evaporation step (6) is fed to the reaction apparatus (1). 15. The process according to claim 14, characterized in that 60 to 85% by weight of the bottoms effluent from the membrane evaporator (5) and the vacuum evaporation step (6) is fed to the reaction apparatus (1).